Abnormal behavior can refer to unusual or statistically rare behavior. For example, recognition of abnormal behavior can be used to detect if an individual has acted or behaved in a manner that suggests abnormality. For example, an individual has fallen at home or work. Abnormal behavior detection is one of the sub-topics of automatic video information searching and content analysis. Main applications of abnormal behavior detection can include, for example, safety of elders at home, and worker protection at working places.